R. C. Rollins (1993) recognized four species in Iodanthus, of which three are endemic to Mexico. As summarized by R. A. Price and I. A. Al-Shehbaz (2001), molecular data clearly support treatment of the genus as monospecific and closely allied to Cardamine, as well as recognition of the three Mexican species as members of Chaunanthus, a genus unrelated to Iodanthus and members of the Thelypodieae.